LDAP Group query always uses scope=one

I'm testing out Group Auth with user attribute `memberOf`.  The entry is as follows.

ldapsearch -x -LLL -H ldap:/// -b "uid=cbman,ou=People,dc=example,dc=com" +

dn: uid=cbman,ou=People,dc=example,dc=com

memberOf: cn=mygroup,ou=Groups,dc=example,dc=com

entryDN: uid=cbman,ou=People,dc=example,dc=com

subschemaSubentry: cn=Subschema

...

Problem is  the LDAP url used to fetch the memberOf attribute doesn't return the group when scope is set to one.

 ~$ curl -user $CREDS "ldap://<host:port>/uid=cbman,ou=People,dc=example,dc=com?memberOf?one"

~$ 

But If I use base or sub, then it works:

 ~$ curl --user $CREDS "ldap://<host:port>/uid=cbman,ou=People,dc=example,dc=com?memberOf?base"
DN: uid=cbman,ou=People,dc=example,dc=com
memberOf: cn=mygroup,ou=Groups,dc=example,dc=com
~${code}

Is there any reason why scope can't be changed for the userAttribute group matching?  I noticed it can be set for 'LDAP Query' option for groups.